This invention relates to a collapsible security grille for screening and freeing at will a doorway, a window reveal, a skylight, the space above a bar or counter, or any other passable opening to which it is desired to deny access at certain times, but not at others.
A known construction of expanding and collapsing security grille comprises, supported in a non-collapsible frame, an array of grille bars consisting of a first set of rigid elongate parallel uniformly spaced-apart grille bars, and a second, similar set in close face-to-face proximity to the first, wherein the grille bars of one set are inclined and disposed with respect to those of the other set to produce meeting points of two grille bars at the periphery of the grille, and to produce crossing points of two grille bars inside said periphery, and also comprises pivotal connectors which interconnect the two adjacent grille bars at each meeting point and crossing point. Such a security grille is herein called a grille of the type described.